Quantcast Appendix A Glossary -Cont. - hdbk419a_vol20344

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PLANE WAVE -- An electromagnetic wave which predominates in the far field region of an antenna, and with
a wavefront which is essentially in a flat plane. In free space, the characteristic impedance of a plane wave is
377 ohms.
RACK -- A vertical frame on which one or more units of equipment are mounted.
RADIATION -- The emission and propagation of electromagnetic energy through space.
RADIATION RESISTANCE -- The resistance which, if inserted in place of an antenna, would consume the
same amount of power that is radiated by the antenna.
RADIO FREQUENCY INTERFERENCE (RFI) -- RFI is manmade or natural, intentional or unintentional
electromagnetic propagation which results in unintentional and undesirable responses from or performance
degradation or malfunction of, electronic equipment.
REFLECTING LOSS -- The portion of the transition loss, expressed in dB, that is due to the reflection of
power at a barrier or shield. Reflection loss is determined by the magnitude of the wave impedance inside the
barrier relative to the wave impedance in the propagation medium outside the barrier.
RF-TIGHT -- Offering a high degree of electromagnetic shielding effectiveness.
SHIELD -- A housing, screen, or cover which substantially reduces the coupling of electric and magnetic fields
into or out of circuits or prevents the accidental contact of objects or persons with parts or components
operating at hazardous voltage levels.
SHIELDING EFFECTIVENESS -- A measure of the reduction or attenuation in the electromagnetic field
strength at a point in space caused by the insertion of a shield between the source and that point.
SIGNAL REFERENCE SUBSYSTEM -- A conductive sheet or cable network/mesh providing an equipotential
reference for C-E equipments to minimize interference and noise.
SIGNAL RETURN -- A current-carrying path between a load and the signal source. It is the low side of the
closed loop energy transfer circuit between a source-load pair.
STRUCTURE -- Any fixed or transportable building, shelter, tower, or mast that is intended to house
electrical or electronic equipment or otherwise support or function as an integral element of an electronics
SUPPORTING STRUCTURES, ELECTRICAL -- Normally nonelectrified conductive structural elements near
to energized electrical conductors such that a reasonable possibility exists of accidental contact with the
energized conductor.  Examples are conduit and associated fittings, junction and switch boxes, cable trays,
electrical/electronic equipment racks, electrical wiring cabinets, and metallic cable sheaths.
TRANSDUCER -- A device which converts the energy of one transmission system into the energy of another
transmission system.


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